Definition & Overview
Iridotomy, also called laser iridotomy or laser peripheral iridotomy, is a laser-based surgical procedure used to treat angle closure glaucoma, a rare eye condition in which the normal fluid circulation of the eye is blocked. With this condition, the iris blocks the trabecular meshwork or drainage site of the eye resulting in the increased pressure in the eye’s front chamber. It also keeps the iris from fully opening.
Termed by some medical literature as acute glaucoma or narrow angle glaucoma, the condition results in various symptoms including recurring headaches, pain in the eye area, blurred vision, and nausea. Some even report seeing rainbows when looking at lights during nighttime.
The procedure can be performed using either an argon laser or Nd:YAG laser or both. The goal of the treatment is to create equal pressure between the anterior and posterior chambers of the eye. This means lowering the intraocular pressure or IOP to avoid damaging the optic nerve and the retina.
Who Should Undergo and Expected Results
The procedure is recommended for patients with angle closure glaucoma, which based on studies, is more prevalent among older women and those with Asian and Eskimo ancestry. The following can also benefit from the procedure:
- Farsighted individuals who are prone to developing angle closure glaucoma
- Aphakic individuals, or those with no intraocular lens
- Patients diagnosed with phacomorphic glaucoma, plateau iris syndrome, aqueous misdirection, pigmentary dispersion syndrome, and nanophthalmos
In some cases, iridotomy is offered as a preventive measure for patients with:
Narrow angles so they do not develop narrow angle closure Pigment dispersion, a condition characterised by the shedding of the iris pigment and its dispersal throughout the anterior chamber of the eye. If left unchecked and untreated, this could lead to pigmentary glaucoma.
Iridotomy works by lowering the intraocular pressure, leading to the normal constriction of the pupil. Monitoring of intraocular pressure is required a few hours after the procedure and patients are given corticosteroid to prevent inflammation of the eye. Patients may be asked to undergo a visual field test to see if there is damage to the optic nerve and other nearby parts of the eye. The procedure has a high success rate and most patients are able to avoid partial or total vision loss.
How is the Procedure Performed?
Iridotomy is not immediately performed on patients diagnosed with acute angle closure. The swelling in the cornea has to subside first and the surgeon has to make sure that the intraocular pressure is significantly lowered before the patient undergoes this procedure. With the use of a topical agent, the pupil is normally constricted prior to surgery to thin the iris.
During the procedure, an iridotomy contact lens is placed in front of the affected eye to help the surgeon direct the laser beam with accuracy. Laser pulses are then applied to the iris until a small hole appears allowing the release of iris material as well as the aqueous fluid. The hole is usually formed in the upper part of the iris, which is covered by the eyelid.
The type of laser to be used in the procedure depends on several factors. Nd:YAG laser is typically used on patients with blue or green-colored irides while those with dark brown irides are treated initially with argon laser before using the Nd:YAG laser. The laser thins out the iris stroma, which is usually thicker with these patients.
Possible Risks and Complications
Iridotomy is linked to various risks and complications, including:
- The sudden increase of intraocular pressure a few hours after the procedure. Thus, patients are monitored following the operation to manage these episodes.
- Inflammation of the anterior chamber of the eye or anterior uveitis. Topical steroids are used to address this condition. If the inflammation does not subside, it could lead to the adherence of the iris to the lens. This condition is called posterior synechia.
- Bleeding, especially if Nd:YAG laser is used
- Hyphema, a condition characterised by the pooling of blood inside the anterior chamber of the eye, leading to partial vision loss. Nearby parts of the eye, including the retina, may also experience bleeding.
- Lens opacities - The use of laser may also cause the development of lens opacities that can lead to full-blown cataract.
- Corneal edema
- Blurred vision
- Double vision
- Light glare
Rosenberg LF, Krupin T, Ruderman J, et al. Apraclonidine and anterior segment laser surgery. Comparison of 0.5% versus 1.0% apraclonidine for prevention of postoperative intraocular pressure rise. Ophthalmology. 1995 Sep. 102(9):1312-8.
Robin AL, Pollack IP, deFaller JM. Effects of topical ALO 2145 (p-aminoclonidine hydrochloride) on the acute intraocular pressure rise after argon laser iridotomy. Arch Ophthalmol. 1987 Sep. 105(9):1208-11.